At present, the subtractive color process is utilized in the silver halide light-sensitive color photographic materials (hereinafter, simply referred to as light-sensitive materials), and color images are formed by combining three prepared dyes employing a yellow coupler, a magenta coupler, and a cyan coupler.
Conventionally, as the magenta couplers employed in the silver halide light-sensitive color photographic materials, there have been known the pyrazolone series, the pyrazolotriazole series, the pyrazolinobenzimidazole series or the indanone series couplers. Of these, various types of 5-pyrazolone derivatives have been widely employed.
As the substituents at the 3-position of the 5-pyrazolone ring of the above-mentioned 5-pyrazolone derivatives, there are employed, for example, an alkyl group, an aryl group, or an alkoxy group described in U.S. Pat. No. 2,439,099, or an acylamino group described in U.S. Pat. Nos. 2,369,489 and 2,600,788, or an ureido group described in U.S. Pat. No. 3,558,319. However, the above-mentioned couplers have resulted in shortcomings such that the coupling reactivity with an oxidized developing agent is low to unable the formation of a magenta dye image with high density; the magenta dye image formed by color development exhibits a large secondary absorption in the blue light region, and the main absorption exhibits no sharp decrease at the long wavelength edge.
The 3-anilino-5-pyrazolone series couplers disclosed in U.S. Pat. Nos. 2,311,081, 3,677,764, 3,684,514, and U.K. Patent Nos. 956,261, 1,173,513, etc. exhibit advantages such as high coupling activity, high dye-forming efficiency, small secondary absorption in the blue region and the like. However, the maximum spectral absorption wavelength of dyes formed employing these 3-anilino-5-pyrazolone series couplers conventionally known in the art positions in the relatively shorter wavelength region. Their use in the silver halide light-sensitive color photographic materials for making color negatives deteriorates the color reproduction on resulting prints. Furthermore, there has been the so-called bleach fog problem, in that after finishing the development process, the oxidized developing agent reacts with the coupler in the bleach bath to cause an increase in fog.
In order to minimize the disadvantage in that the maximum spectral absorption wavelength of the formed dye occupies a position in the short wavelength region, various investigations have been made. As a result, 1-pentahalogenophenyl-3-anilino-5-pyrazolone series couplers are proposed in Japanese Patent Publication Open to Public Inspection No. 52-80027. Dyes prepared employing the above-mentioned couplers exhibit the maximum spectral absorption wavelength more preferably as compared to conventional couplers. However, these couplers have exhibited disadvantages such that the dye-forming efficiency is not sufficient enough, and the maximum spectral absorption wavelength of the formed dye depends on the density (so-called dichroism).
Furthermore, German Patent 19,525,666 discloses 4-(2-N-alkylsulfonamide)phenylthio-5-pyrazolones. However, these compounds have been found to be unsatisfactory, because image dyes formed employing these compounds exhibit disadvantages such that the maximum spectral absorption wavelength varies in accordance with the density, that is, dichroism is caused; the color reproduction is degraded because the maximum spectral absorption wavelength occupies a position in the shorter wavelength region and is not adapted to that of the conventional couplers for color negative film and that low sensitivity and low dye formation efficiency result.
The feature of the present invention is that a 3-anilino-4-arylthio-5-pyrazilone coupler comprises both a specified ballast (substituent of 3-anilino part) part (hereinafter referred to as a ballast) and a 4-arylthio group (hereinafter referred to as a coupling point substituent). The ballasts of the present invention are described in Japanese Patent Publication Open to Public Inspection Nos. 8-171186 and 7-82626. However, in those specifications, there is not described any of the coupling point substituent of the present invention, and based on the description, it is difficult to hit on the coupling point substituent. Further the couplers described in the above-mentioned patent have the disadvantage of high bleach fog, and the couplers of the present invention are clearly superior to those couplers.
Furthermore, German Patent No. 19,525,666 discloses couplers having a ballast (exemplified compound M-4=comparative compound of the present invention M-9) having a structure similar to the coupler of the present invention. However there is described no photographic performance. The inventors of the present invention traced the coupler and found the disadvantages such as low dye forming efficiency, large dichroism, and the like. In the specification of the above-mentioned patent, a ballast similar to the structure of the ballast of the present invention is only employed in compound M-4 and it is impossible to get technical concept to employ the ballast of the present invention. There is no description on the superiority obtained by employing the ballast of the present invention. Based on the description in Examples of the present invention, it will definitely be seen that the couplers of the present invention based on a technical concept not suggested in the above-mentioned German Patent exhibit surprisingly higher performance than those described in the above-mentioned German Patent.